Windows 10: How do I reactivate my Windows 10 Pro Copy?

I bought a refurbished HP Z420 workstation a year ago, almost to the day of posting, but at some point stuff wasn’t working right, and a friend recommended reseting the PC. The trick seemed to work, but at the cost of an ugly watermark in the bottom of the screen claiming windows needed to be activated. I thought this wasn’t a problem, since I only seemed to lose the ability to change wallpapers.Roughly half a week ago, I needed to update Minecraft Bedrock Edition, and the launcher was stuck on “Waiting for install”, and no online help seemed to work. So, a different friend recommended I resta

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Motherboard change unable to reactivate Windows 10 Pro -

I have searched this topic and everything seems to be almost a year old. This is a homebuilt machine circa 2015. It started with an ASUS FM2+ motherboard with an AMD A5600K processor. It was Windows 7 Pro, upgraded to Windows 8.1 Pro then to Windows 10 Pro.
Saturday the motherboard died. An exact replacement could not be located so a Gigabyte card was installed. No changes to the hard drives. Booted the machine and Windows automatically started and then did a "revert" then installed the latest updates. C Drive was in the red so I deleted all of the old install files using Windows Clean-up. Went to reactivate, checked the significant hardware change and entered my MS account information - The computer (none of my computers) were listed and now it is telling me that I have to spend $200 to buy a copy of Windows 10 Pro.
Have not yet called Customer Support as the computer is at home and I work during the day -
I do have a disk image or two that may be a year old -

Suggestions - should I just shell out the $200 and move on

TIA

 

Motherboard change unable to reactivate Windows 10 Pro -

Activate using windows 7 pro key.

 

Reactivation Windows 10 Pro issue

I have changed my hardware recently and found that I can't reactivate Windows 10 Pro. In Reactivate Windows section, I can't find my current device in the list, only my old motherboards appeared ( MSI and Gigabyte ). My old hardware are I7-4790 + MSI H81M
Mobo + 8GB DDR3 Ram and I upgraded to I5-9400F + My new Asrock MOBO B350 or 450 something (Can't remember) + 16 GB DDR4 Ram. There is no my current MOBO in the reactivate section, only the old one appeared (MSI H81M Mobo). Pls someone help me.

Also note that I have signed in with my microsoft account that links with Windows 10 pro licence but it only shows the old mobo in the reactivate list.